diff --git a/tests/server.py b/tests/server.py
index b9ccde4962db7277010c9a52ccd4ac8203f48fed..a74fb3fc6751fd32bb7c0b703503bf15e424878b 100644
--- a/tests/server.py
+++ b/tests/server.py
@@ -193,6 +193,8 @@ def make_request(
     if not path.startswith(b"/"):
         path = b"/" + path
 
+    if isinstance(content, dict):
+        content = json.dumps(content).encode("utf8")
     if isinstance(content, str):
         content = content.encode("utf8")
 
diff --git a/tests/unittest.py b/tests/unittest.py
index 8c7979a7c072c9c5557636b294558d707b676e6f..3e656b7b1248aa6dd257854530760595306aa5c9 100644
--- a/tests/unittest.py
+++ b/tests/unittest.py
@@ -429,9 +429,6 @@ class HomeserverTestCase(TestCase):
         Returns:
             Tuple[synapse.http.site.SynapseRequest, channel]
         """
-        if isinstance(content, dict):
-            content = json.dumps(content).encode("utf8")
-
         return make_request(
             self.reactor,
             self.site,